Animal food products with a dual texture of this kind are well-known in the art. WO 02/052951 A1, for example, describes a co-extruded, dual-component animal food product with an outer component containing at least 60% cereal, and an inner cream-textured component that has water-soluble components in an aqueous phase, which form a stable emulsion with a lipid-free hydrocarbon phase.
WO 00/74496 A1 describes a pack of animal food product consisting of an outer dry shell and an inner moist core, the core and the shell being separated from one another by a moisture-resistant barrier layer.
FR 2265287 A discloses an animal food product comprising a filling which is completely surrounded by a cereal-containing expanded extrudate. The filling contains meat, sugar, vegetable materials and an effective amount of a mycostatic agent. The filling material has a moisture content of 15-40 percent by weight and a water activity (aw) of 0.70-0.90.
Animal food products with a dual texture, namely a soft and moist core and a dry and allegedly crispy shell are thus known from the state of the art. It has, however, been found that none of the animal food products known so far does in fact provide a clear and lasting delimitation between the soft core and the harder shell. On the contrary, in the known animal food products, the transition between the soft core and the hard shell is more or less fluid; especially after a lengthy storage time, the texture of the two components becomes so similar that it is hardly possible to perceive a difference between the core and the shell. This is presumably due to a diffusion of the moisture from the core into the shell. The disappearance of the difference between the core and the shell also has a particular influence on the microbiological safety of the animal food product (especially when it has a high moisture content) and the oxidative stability of any fat components that might be contained in the material of the core.
U.S. Pat. No. 4,777,058 A discloses a method of producing an animal food composition which likewise possesses a soft core and a harder shell. That animal food composition is produced by first of all extruding the components of the shell through an annular die in the form of a continuous cavity. The components of the core are then extruded into a portion of the extruded shell after a certain time has passed, which must be sufficient for the shell to become solid enough to withstand the pressure of the core components injected.
EP 1063897 B1 discloses a pet or animal food product with a dual texture and a method of producing same. That pet or animal food product has a shell component which completely encloses an inner component. The production method is that of co-extrusion.
For the production of the animal food products described, the extrusion and in particular the co-extrusion of components in an extruder device for a wide variety of materials may, however, involve problems. For continuous and reliable production, it is necessary to set a particular viscosity of the materials to be extruded, such as by means of a particular choice of temperature, so that the materials can be fed through the extruder. In addition, it is necessary to ensure that the extrusion dies used do not become clogged, as can easily happen in particular when semi-solid materials are to be extruded which may optionally still contain some pieces of solid material.
It is the object of the present invention to provide a method of producing an animal food product with a core and a shell at least partially covering the core, with which the disadvantages of the prior art can be overcome. In particular, it is intended to provide a method which dispenses with the extrusion of components of the animal food product and makes it possible to produce the animal food product in an extremely simple manner. The animal food product should preserve a distinct difference in texture between the shell and the core over a long period, especially including when the packaging of the animal food product has been opened; it should guarantee microbiological safety even in the case of a high moisture content on the part of the core material and should exhibit oxidative stability for a core material with a high proportion of fat. The difference in texture between the core and the shell should be distinctly perceptible to the user.